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The Urinary System

Kidney, bladderThe organs, tubes, muscles and nerves that work together to create, store and carry urine are the urinary system. The urinary system includes two kidneys, two ureters, the bladder, two sphincter muscles and the urethra.

Your urinary system works to excrete waste products from your body and to keep the chemicals and water in your body balanced. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) says adults eliminate about a quart and a half of urine each day. The amount depends on many factors, including how much you eat and drink and how much fluid is lost through sweat (Read about "Sweating") and breathing. Certain types of medications can also affect the amount of urine eliminated.

The urinary system removes a type of waste called urea from your blood. Urea is produced when foods containing protein are broken down in the body. Urea is carried in the bloodstream to the kidneys. The kidneys remove urea from the blood through tiny filtering units called nephrons. From the kidneys, urine travels down two thin tubes called ureters to the bladder. The bladder is a hollow muscular organ in your pelvis. It stores urine until you are ready to go to the bathroom to empty it. The urethra is the tube that lets urine pass outside the body. Nerves (Read about "Nervous System") in the bladder let you know when it is time to do this. Until then, muscles called sphincters help keep urine from leaking by closing tightly around the opening of the bladder into the urethra.

Diseases and conditions

Problems in the urinary system can be caused by aging, illness or injury. As you get older, changes in the kidneys' structure cause them to lose some of their ability to remove wastes from the blood. Also, the muscles in your ureters, bladder, and urethra tend to lose some of their strength as you age.

Urologists are doctors who treat diseases and conditions of the urinary system in both men and women, as well as the male reproductive system. (Read about "Genital Health - Male" "Reproductive Health") Urological diseases and conditions include:


Urinalysis is a test that studies the content of urine for abnormal substances such as protein or signs of infection. This test involves urinating into a special container and leaving the sample to be studied. Protein is a major building block that our body uses to build muscle. Normally the kidneys leave protein in the blood. If protein shows up in your urine (proteinuria), it may indicate problems with the kidneys. Your glomerular filtration rate (GFR) is a measure of how well your kidneys are filtering wastes from your blood. Your GFR can be estimated from a routine measurement of creatinine in your blood.

Urodynamic tests evaluate the storage of urine in the bladder and the flow of urine from the bladder through the urethra. Your doctor may want to do a urodynamic test if you are having symptoms that suggest problems with the muscles or nerves of your lower urinary system and pelvis - ureters, bladder, urethra and sphincter muscles. Urodynamic tests measure the contraction of the bladder muscle as it fills and empties. The test is done by inserting a small tube called a catheter through your urethra into your bladder to fill it either with water or a gas. Another small tube is inserted into your rectum or vagina to measure the pressure put on your bladder when you strain or cough.

Renal imaging procedures can also be used. X-rays (Read about "X-rays") of the urinary tract can help highlight a kidney stone or tumor that could block the flow of urine and cause pain. An x-ray can also show the size and shape of the prostate. X-rays can also be combined with contrast material. For example, in intravenous pyelogram (IVP), a contrast medium is injected into a vein, and followed as it circulates through the blood and reaches the kidneys. In voiding cystourethrogram (VCUG), a catheter inserted in the urethra is used to fill the bladder with a contrast medium, which can then be watched on video during urination. Other imaging tests such as ultrasound, CT scan or magnetic resonance imaging (Read about "Ultrasound Imaging" "CT Scan - Computerized Tomography" "MRI - Magnetic Resonance Imaging"), are also used.

All Concept Communications material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.

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